Function isRetryableCode

isRetryableCode(code: string): boolean | undefined
Is this BusError code a transient (retryable) failure? Consults the registry. Returns undefined for codes not in ERROR_CODE_REGISTRY.
Parameters
- code: string
Returns boolean | undefined
Example
```
if (result.error instanceof BusError && isRetryableCode(result.error.code) === false) {
  // permanent failure — don't re-dispatch
}
```
- Defined in schema.ts:625